Abstract
A low power 22-mW 900MHz Frequency Synthesizer (FS), with an on-chip LC-tuned voltage controlled oscillator (VCO) for GSM applications is presented. The synthesizer possesses several novel features that include a completely integrated structure, a low phase noise on-chip LC VCO, a low-power Dual-Modulus Divider (DMD) in CML topology, a compensated charge pump with balanced switching, an on-chip third order loop filter and a proposed relatively easy to implement fractional accumulator based frequency synthesis technique. The complete synthesizer achieves in-band phase noise characteristics better than -110 dBc/Hz at 100kHz offset. The channel switching time is less than 500mus for a 25MHz frequency hop. The synthesizer is able to accommodate all 195 transmit and receive channels in the R-GSM band. The proposed architecture has been realized using the 0.5 mum AMI C5N technology. The complete integrated synthesizer occupies less than 1500 x 700 mum(2) of die real estate.